Heating apparatus



May 21, 1935. N. L. BLACKMORE HEATING APPARATUS Filed Dec. 5, 1930 2 Sheets-Sheet 1 J0 WET/amen Wk, MC M I Patented May 21, 19.35

HEATING APPARATUS Norman L. Blackmore, Vllillrinsburg, Pa., assignor to Automatic Gas-SteamBadiator Company, Pittsburgh, Pa., a corporation of Pennsylvania Application December a, 1930. Serial No. 499,725

1Claim.

My invention relates, in general, to heating devices and, in particular, to air heaters adapted to be suspended from an overhead support for use in shops, factories, and the like.

An example of this type of heater as constructed heretofore is afforded by the United States Patent 1,754,952, to Humphery. It is the object of this invention to improve upon the-construction and arrangement of parts characterizing the devices previously known. The particular improvement contemplated by the invention concerns the arrangement of the duct for exhausting burnt v the chamber is formed by a flanged plate I6 suitgases from the combustion chamber.

Heaters of the type mentioned are generally gasfired and are provided with a combustion chamber, a heating chamber, and an off-take or exhaust box for theburnt gases. The hot gases from the burners pass through heat-transfer tubes in the heating chamber and air is circulated around the tubes by means of a fan driven by an electric motor. In the embodiment shown in the drawings, I arrange the construction of the combustion chamber so that an inlet for secondary air is provided at the bottom thereof. The offtake or exhaust box for burnt gases is provided with a vent for the relief of back drafts in the stack. The tubes conducting the hot gases frgm the burners are provided with a spiral bafiie to prevent too rapid passage of the gases therethrough and to insure that the hot gases have intimate contact with the walls of the tubes. I have shown, furthermore, means for automatically controlling an electro-magnetic valve for admitting fuel to the burners so as to prevent opening of the valve if the pilot burner is not lighted. A novel form of pilot burner is also included in the device and is constructed so as to prevent the flame from being blown back into the interior of the burner, for example by a back draft. By my invention I provide means whereby the circulating fan is effective to increase the draft through the combustion chamber and transfer tubes.

For a complete understanding of the invention, reference is made to the accompanying drawings which illustrate a present preferred embodiment of the invention, although it is to be understood that the drawings constitute no limitation upon the scope of the invention since it may be otherwise embodied within the scope of the claim.

In the drawings,

Figure 1 is a side elevation of a preferred form of the invention, parts thereof being shown in section;

the line IIII of Figure 1, showing parts in ele' vation with the fan and its motor removed.

Referring in detail to the drawings, the heating device constructed in accordance with my invention comprises a combustion chamber III, a heating chamber I I, and a gas off-take or exhaust box l2. The device is adapted to be supported from overhead on hangers l3 suitablysecured to various portions thereof.

The combustion chamber III is provided with end walls l4 and side walls IS. The bottom of ably secured to the side walls 15. The bottom plate I6 extends laterally beyond the side walls l5 and is spaced therebeiow to provide inlets I1 adjacent the bottom of the chamber for secondary air.

Burners l8 and I9 are suitably supported in the combustion chamber Ill and are connected through individual manually operated valves I81: and l 9a and a main electro-magnetic valve 2i to a gas supply conduit 22. A pilot burner 23 is also located within the combustion chamber and is connected through a valve 24 to the gas supply.

The top wall of the combustion chamber I0 is formed by a perforated plate 26 which also constitutes the bottom wall of the heating chamber l l. The chamber I I is open on both sides but has its end walls formed by sheet metal panels 21 secured, to the hangers 13. At one side of the chamber Ii, a plurality of deflecting vanes 28 are pivoted between opposite hangers l3. The other side of the chamber is covered by an annular shell 29 secured to the hangers l3. A frame 30 is secured to the shell 29 and carries a guard cage 3| for a fan 32 therewithin. The fan 32 is adapted to be driven by a motor 33 supported on the frame 30. A junction box 34, mounted on the shell 29, provides electrical connections for the motor 33.

A perforated plate 35 bolted to the hangers l3 forms the top wall of the heating chamber 1 l. A plurality of heat transfer tubes 36 extend between the plates 26 and 35 for conducting hot gases from the combustion chamber through the heating chamber. In order to prevent too rapid passage of hot gases through the tubes 35, and to insure intimate contact of the gases with the walls of the tubes, I prefer to insert a spiral bame 31 in eachof the tubes 36. The baflles may be supported on lugs 38 bent down from the end thereof so as to engage the upper ends of the tubes. The baflies cause the hot gases arising through the tubes to travel in a spiral path around the tube and to have intimate contact with the walls thereof. High efliciency of heat transfer is thus obtained.

In order to overcome the obstruction to nat ural draft from the combustion chamber through the tubes, caused by the baflles 31, I provide the plate 36 with a centrally disposed hole. A tube of elbow shape flts in the hole and directs a portion of the blast created by the fan through the offtake II. The tube 35a may be provided with-a damper to facilitate control of the additional draft created by the fan.

The tubes 36 lying in the space traversed by the tube 3611 are shortened and connected to the latter. The hot gases flowing into the tube 35a from the tubes 36 further increase the natural draft of the system. The plate 35 would have holes only for those of the tubes 36 which extend the entire distance between the plates 26 and 35.

A hood 39 secured to the hangers I3 overlies the plate 35 and extends laterally therebeyond to provide back draft vents 40 in the off-take l2. The off-take may be connected to a stack through an outlet 4| and a funnel duct 42 having a conical bailie 43 therein. An alternative outlet is shown at Ma.

when the device is to be started in operation,

I the pilot 23 is lighted after opening its valve 24.

A circuit is then completed for the motor 44 for operating the valve 2|. When the valve 2| is open, the pilot burner 23 will ignite the burners l8 and I9 and the operating switch will start the motor 33 so that the fan 32 will circulate air around the heat transfer tubes 36.

It will be apparent from the foregoing description that the invention described is characterized byv advantages over devices of this type known heretofore. The transfer of heat from the hot combustion gases to the air is made more eflicient by the spiral baflies in the heat transfer tubes. The natural draft through the device is supplemented by a forced draft from the circulating fan.

Although I have illustrated and described but one present preferred embodiment of the invention, it may be otherwise embodied within the scope and spirit of the appended claim.

I claim:

A unit heater of the character described, comprising a combustion chamber, fuel burning means therein, an exhaust chamber spaced from the said combustion chamber, a plurality of heat transfer tubes communicating with and extending between said combustion chamber and said exhaust chamber, means for circulating fluid over the outer surfaces of said tubes and a conduit communicating with said exhaust chamber for causing a portion of said circulating fluid to supplement the natural draft from the combustion chamber to the exhaust chamber, said conduit communicating with at least one of said heat transfer tubes outside of said exhaust chamber.

NORMAN L.'BLACKMORE. 

